KR102356876B1 - Hot melt adhesive composition and uses thereof - Google Patents

Abstract

A sprayable olefinic hot melt adhesive and an absorbent article comprising the adhesive are disclosed. The sprayable olefinic hot melt adhesives are particularly suitable for spraying at low application temperatures. The sprayable low application temperature hot melt adhesive has high green strength, excellent bonding strength and aging performance. In addition, the sprayable low application temperature hot melt adhesive enables thin bond lines without the risk of bleed-through and burning to heat-sensitive substrates.

Description

Hot melt adhesive composition and uses thereof

The present invention relates to sprayable olefinic hot melt adhesives and absorbent articles comprising the adhesives. The sprayable olefinic hot melt adhesives are particularly suitable for spraying at low application temperatures.

Hot melt adhesives play an important role in the manufacture of wearable absorbent articles such as diapers, sanitary napkins, and adult incontinence briefs. In these applications, an adhesive is applied to at least one substrate, such as, for example, a film substrate, a nonwoven substrate or an elastic substrate, to bond the substrate to a second, similar or different substrate. Upon cooling, the adhesive cures to bond the substrates together.

Conventional hot melt adhesives based on rubber block copolymers and/or olefin copolymers are usually applied at temperatures in excess of 155°C (311°F). Reducing the application temperature of the adhesive used in the manufacture of the product to 155°C or lower improves heat aging in the applied equipment, improves the safety of equipment operators, and prevents defective products due to the inclusion of heat-sensitive substrates in the product. will decrease A hot melt adhesive suitable for such low application temperatures should have a low viscosity below 155°C. Lower molecular weight polymers and higher diluent concentrations have been used to reduce the viscosity of conventional adhesives at the expense of hot melt adhesive performance. This approach results in lower mechanical strength and, more importantly, poor resistance to flow at elevated temperatures. As another approach to reducing viscosity, adding a wax or other low molecular weight crystalline component results in an adhesive with reduced effective open time.

Although metallocene catalyzed polypropylene copolymer based hot melt adhesives provide good adhesion to a variety of substrates; Due to the high viscosity of the metallocene catalyzed polypropylene copolymer, such adhesives are not suitable for spraying at low application temperatures. Adhesives made from amorphous poly alpha olefin (APAO) copolymers have lower viscosities and can be sprayed at lower application temperatures; Such adhesives have poor green strength and long open times. Additionally, APAO-based adhesives often fail to form bonds of adequate strength for making disposable articles.

There is a continuing need for hot melt adhesives that have low viscosity and form strong bonds to a variety of substrates that can be applied at low temperatures, ie, less than about 155°C. Such properties would make the adhesive particularly well suited for use in the manufacture of disposable articles. The present invention is directed to this need.

[Summary of the invention]

The present invention provides a sprayable low application temperature hot melt adhesive. The sprayable low application temperature hot melt adhesive has high green strength, excellent bonding strength and aging performance. In addition, the sprayable low application temperature hot melt adhesive enables thin bond lines without the risk of bleed-through and burn through to heat-sensitive substrates.

In one embodiment, the sprayable low application temperature hot melt adhesive comprises:

(a) (i) a propylene content of from about 70 to about 95 weight percent of the (co)polymer, (ii) a polydispersity (Mw/Mn) value of less than about 3.0, (iii) 230° C. as measured according to ASTM D1238 a melt flow rate of from about 20 to about 300 g/10 minutes at /2.16 kg, (iv) a melting point of less than about 90° C. as measured according to ASTM 3418, and (v) 10° C./ as measured according to ASTM D3418-12 from about 5 to about 40 weight percent of a polypropylene-polyethylene (co)polymer having a heat of fusion value of less than about 35 J/g at heating and cooling rates of minutes;

(b) from about 30 to about 70 weight percent of a tackifier; and

(c) optionally up to about 30% by weight of a wax or plasticizer.

The adhesive has a tan δ value greater than about 30 at 140° C., 10 rad/s, and a melt (Brookfield) viscosity of about 2,000 to about 11,000 cps at 150° C., ASTM 3236-88.

In another embodiment, the sprayable low application temperature hot melt adhesive consists essentially of:

(a) (i) a propylene content of from about 70 to about 95 weight percent of the (co)polymer, (ii) a polydispersity (Mw/Mn) value of less than about 3.0, (iii) 230° C. as measured according to ASTM D1238 a melt flow rate of from about 20 to about 300 g/10 minutes at /2.16 kg, (iv) a melting point of less than about 90° C. as measured according to ASTM 3418, and (v) 10° C./ as measured according to ASTM D3418-12 from about 5 to about 40 weight percent of a polypropylene-polyethylene (co)polymer having a heat of fusion value of less than about 35 J/g at heating and cooling rates of minutes;

(b) from about 30 to about 70 weight percent of a tackifier;

(c) up to about 50% by weight of an amorphous poly alpha olefin polymer; and

(d) up to about 30 weight percent wax or plasticizer.

The adhesive has a tan δ value greater than about 30 at 140° C., 10 rad/s, and a melt (Brookfield) viscosity at 150° C. of about 2,000 to about 11,000 cps as measured according to ASTM 3236-88.

Another aspect of the invention relates to an article of manufacture comprising the sprayable low application temperature hot melt adhesive described herein. The article comprises a film substrate, a nonwoven substrate or an elastic substrate bonded together using a sprayable low application temperature hot melt adhesive. Articles of manufacture encompassed by the present invention include wearable absorbent articles such as diapers, sanitary napkins, adult incontinence pants, and the like.

Another aspect of the present invention is a method comprising the steps of spraying a sprayable low application temperature hot melt adhesive composition of the present invention onto a first substrate at a temperature of about 155° C. or less, contacting the second substrate with the adhesive composition applied to the first substrate. and cooling to form a bond.

"Absorbent article" refers to a device that absorbs and contains body exudates, and more specifically refers to a device positioned opposite or proximate to the body of a wearer to absorb and contain various exudates released from the body. . Exemplary absorbent articles include diapers, training pants, pull-on pant-type diapers (i.e., diapers having pre-formed waist and leg openings as exemplified in US Pat. No. 6,120,487); refastenable or pant-type diapers, incontinence pants and undergarments, diaper holders and liners, feminine hygiene garments such as panty liners, absorbent inserts, and the like.

“Adhesively bonded” refers to a substrate to which an adhesive is used to bond a substrate (eg, film, elastomeric film, nonwoven), or a second similar or different substrate.

“Aging” performance (such as “aging bond strength”) refers to a measurement obtained after storing a sample at 50° C. for 2 weeks. "Initial bond strength" performance refers to a measurement obtained within one day after sample preparation.

“Bleed-through” describes the phenomenon in which the applied adhesive seeps out of the applied area of the substrate prior to curing.

"Burn-through" describes a phenomenon in which the heat of the applied adhesive results in defects such as wrinkles or holes in the substrate.

"Include", "comprising" and "comprising" are open-ended terms, each enumerating what follows, such as the presence of a component, but other features known in the art or disclosed herein, such as an element; It does not exclude the presence of steps or components.

As used herein, “consisting essentially of” and “consisting essentially of” refer to the materials or steps recited as in the claims, and those that do not materially affect the basic and novel characteristics of the subject matter. It is used to limit the area.

"Low application temperature" refers to applying the adhesive at or below 155°C.

"Polydispersity Index" (PDI) refers to the distribution of molecular mass in a polymer. PDI is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). As the polymer chain approaches a uniform chain length, the PDI approaches a value of 1.

The present invention provides a sprayable hot melt adhesive that can be applied at or below 155°C. Such sprayable hot melt adhesives have high green strength and excellent bonding strength upon cooling and aging performance. The sprayable hot melt adhesive can be applied to heat-sensitive substrates with a thin bond line without the risk of bleed-through and burn-through.

The term “polymer component” as used herein refers to a single propylene (co)polymer, or a blend of different (co)polymers, produced by metallocene catalyzed polymerization. The (co)polymer component includes block and/or random polypropylene. The propylene (co)polymer is a propylene copolymer with at least one comonomer selected from C ₂ , C ₄ -C ₂₀ comonomers. Preferred comonomers are ethylene, butene, hexene and octene.

The polypropylene (co)polymer has a melt flow rate of from about 20 to about 300 g/10 min, preferably from about 40 to about 150 g/10 min at 230°C/2.16 kg as measured according to ASTM D1238. It has been found that polypropylene (co)polymers with this series of melt flow rates provide good green strength and flexibility for sufficient open time while tuning cohesive strength and elasticity for good bonding performance.

In another embodiment, the propylene (co)polymer has a PDI value of less than about 3.0, preferably less than 2.5. Such homogeneous polymers are typically prepared by metallocene catalysts that impart narrow molecular weight and composition distribution and stereospecificity.

The propylene (co)polymer is greater than about 70 weight percent based on the (co) polymer, preferably from about 70 to about 95 weight percent, more preferably from about 75 to about 92 weight percent, even more preferably from about 81 to about 91 weight percent. % by weight of propylene. This range of propylene content of the (co)polymer provides better adhesion on a variety of substrates. In addition, adhesives prepared in this (co)polymer propylene content range can better withstand heat and aging conditions.

In another embodiment, the polypropylene (co)polymer has a melting point of less than about 90 °C, preferably less than about 70 °C, more preferably less than about 65 °C as measured according to ASTM 3418.

Preferably, the metallocene catalyzed polypropylene (co)polymer has random rules with no specific rules for the polymer structure. Random polypropylene (co)polymers are described as having a semi-crystalline structure, especially in the copolymer, containing low crystallinity. The term "semi-crystalline" as used in polypropylene (co)polymers indicates that the polymer contains both crystalline and amorphous regions in the solid state. In the crystalline region, the molecular chains of a polymer are all arranged in a regular three-dimensional arrangement whose structure can be fully characterized by its unit cell, which is the smallest structural unit used to describe a crystal. On the other hand, the amorphous region does not have a regular three-dimensional structure in the solid state. Its molecular chains are arranged in a completely random way in space. Semi-crystalline polypropylene (co)polymers can be obtained from polymers that are completely amorphous by observing the presence or absence of a melting point (Tm) and associated enthalpy or heat of fusion (ΔHm) resulting from the transformation of the crystalline state to the liquid state upon heating. can be easily distinguished. All semi-crystalline polymers exhibit a melting point, whereas amorphous polymers do not. Amorphous polymers undergo a transition from a glassy solid to a rubbery elastic state in a narrow temperature range around the glass transition temperature Tg. The glass transition temperature Tg should not be confused with the melting point Tm. Unlike the melting transition of crystalline materials, the glass transition of amorphous polymers does not have an associated enthalpy change peak (ΔHm).

The polypropylene (co)polymer has a heat of fusion value of less than about 35 J/g, preferably less than 20 J/g, more preferably less than about 15 J/g, as measured according to ASTM D3418-12. The heat of fusion is defined as the change in enthalpy for the conversion of a specified amount of a solid to a liquid at constant pressure and temperature, and is reported as ΔHm from the DSC measurement. The heat of fusion is directly correlated with the crystallinity of the polymer. A low level of crystallinity is preferred for the polypropylene (co)polymer of sprayable hot melt adhesives.

Propylene (co)polymers are available from various manufacturers: VERSIFY (Dow Chemical), VISTAMAXX (Exxon Mobil), TAFMER (Mitsui Petrochemical) (Mitsui Petrochemical), L-MODU (Idemitsu), NOTIO (Mitsui), etc. can be purchased under the trade names.

The polypropylene (co)polymer content in the sprayable low application temperature hot melt adhesive ranges from about 5 to about 40 weight percent, based on the total weight of the adhesive.

Surprisingly, (i) a melt flow rate of from about 20 to about 300 g/10 min as measured by 230°C/2.16 kg ASTM D D1238, (ii) a polydispersity (Mw/Mn) value of less than about 3.0, (iii) ( a propylene content of from about 70 to about 95 weight percent of the co)polymer, (iv) a melting point of less than about 90° C. as measured according to ASTM 3418, and (v) 10° C./min as measured according to ASTM D3418-12. Adhesives made using polypropylene having the specific parameters of a heat of fusion value of less than about 35 J/g at heating and cooling rates are sprayable at low application temperatures, such as 155° C. or lower, and have high green strength, bond strength and It has aging performance.

The adhesives of the present invention may optionally contain up to about 50 weight percent amorphous poly alpha olefin (APAO). The amorphous poly alpha olefin has a polydispersity index greater than 3.0, which is higher than the metallocene catalyzed (co)polymer. Amorphous poly-α-olefin polymers are random copolymers or terpolymers of C ₂ to C ₂₀ monomers, specifically including ethylene, propylene, butene and octene, and other substantially amorphous or semi-crystalline propylene-ethylene polymers. do. Commercially available APAOs suitable for use in adhesives include Rextac (Rexene LLC), Eastoflex (Eastman Corpoartion) and Vestoplast (EVO). Evonik Corporation).

Sprayable low application temperature hot melt adhesives also include a tackifier. Useful tackifying resins include any compatible resin or mixtures thereof such as aliphatic petroleum hydrocarbon resins; aromatic petroleum hydrocarbon resins and hydrogenated derivatives thereof; and alicyclic petroleum hydrocarbon resins and hydrogenated derivatives thereof. Examples of particularly suitable hydrogenated aliphatic adhesives include Escorez 5400 from Exxon Mobil Chemicals, Arkon P115 from Arakawa, and Eastotac 130R, Regalite S1100 from Eastman Chemicals, etc. This is included. Also included are cyclic or acyclic C ₅ resins, and aromatic modified acyclic or cyclic resins. Examples of commercially available C ₅ resins include Cray Valley USA LLC's Wingtack extra, Wingtack ET, Eastman Chemical's Piccotac 9095, Exxon Mobil Chemicals' Escorez 2203 LC, Luhorez A1100, A2100 from Luhua Chemical Corp. Also included are polyterpene resins; Examples are phenolic modified terpene resins and hydrogenated derivatives thereof, including resin products resulting from the condensation of bicyclic terpenes and phenols in an acidic medium. Examples of commercially available rosins and rosin derivatives that may be used in practicing the present invention include SYLVALITE RE 110L and SYLVARES RE 115 available from Arizona Chemical; Dertocal 140 from DRT; Limed Rosin No. 1, GB-120 and Pencel C from Arakawa Chemical. Examples of commercially available phenolic modified terpene resins are Silvareth TP 2040 HM and Silvareth TP 300, both available from Arizona Chemicals. Other useful tackifying resins include, for example, natural and modified rosins including gum rosin, woody rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, lesinate and polymerized rosin; Glycerol and pentaerythritol of natural and modified rosins including, for example, glycerol esters of light woody rosins, glycerol esters of hydrogenated rosins, glycerol esters of polymerized rosins, pentaerythritol esters of hydrogenated rosins and phenol-modified pentaerythritol esters of rosins ester; Examples include copolymers and terpolymers of natural terpenes including styrene/terpenes and alpha methyl styrene/terpenes.

Preferred tackifiers include C ₅ resins, petroleum distillates, hydrogenated hydrocarbons, C ₅ /C ₉ resins, C ₉ resins, polyterpenes, rosins, hydrogenated rosins, rosin esters and mixtures thereof.

In one embodiment, the tackifier is a synthetic hydrocarbon resin. Included are aliphatic or cycloaliphatic hydrocarbons, aromatic hydrocarbons, aromatically modified aliphatic or cycloaliphatic hydrocarbons and mixtures thereof. Non-limiting examples include aliphatic olefin-derived resins such as those available under the trade name of the Escorez series from Exxon, the Wingtag series from Cray Valley USA LLC and the Eastman series from Eastman are also useful in the present invention.

Also useful are aromatic hydrocarbon resins that are C ₉ aromatic/aliphatic olefin-derived and commercially available from Sartomer and Cray Valley under the trade name Norsolene and from Rutgers as the TK aromatic hydrocarbon resin series. . Norsolene 1100 is a low molecular weight thermoplastic hydrocarbon polymer commercially available from Cray Valley.

Alpha methyl styrenes such as Kristalex F 115, 1120 and 5140 from Eastman Chemicals and Silvareth SA series from Arizona Chemicals are also useful as adhesives in the present invention. For some formulations, a mixture of two or more of the tackifying resins described may be required.

In one embodiment, the tackifier is typically present at about 30 to about 70 weight percent, more preferably about 35 to about 65 weight percent, more preferably about 40 to about 60 weight percent, based on the total weight of the adhesive.

The sprayable low application temperature hot melt adhesive optionally includes a wax. Useful waxes have a heat of fusion greater than 50 J/g at a heating and cooling rate of 10° C./min as measured according to ASTM D3418-12 by DSC.

Waxes suitable for use in sprayable low application temperature adhesives include paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, by-product polyethylene wax, Fischer-Tropsch wax, oxidized Fischer-Tropsch wax and functionalized waxes such as hydroxy stearamide waxes and fatty amide waxes. High density low molecular weight polyethylene waxes, by-product polyethylene waxes and Fischer-Tropsch waxes are commonly referred to in the art as synthetic high melting point waxes. Useful waxes include polyethylene and polypropylene waxes available from Clariant in the LICOCENE series, Sasol in the Sasol, and in the AC series from Honeywell.

The wax component may be present in an amount of up to about 30% by weight based on the total weight of the sprayable low application temperature hot melt adhesive.

The sprayable low application temperature hot melt adhesive also optionally comprises up to 30 wt % of a plasticizer based on the total weight of the sprayable low application temperature hot melt adhesive. Suitable plasticizers include polybutenes, polyisobutylenes, phthalates, benzoates, adipic acid esters, and the like. Particularly preferred plasticizers include mineral oils, aliphatic oils, olefinic oligomers and low molecular weight polymers, vegetable oils, animal oils, paraffinic oils, naphthenic oils, aromatic oils, long chain partial ether esters, alkyl monoesters, epoxidized oils, dialkyl di Esters, aromatic diesters, alkyl ether monoesters, polybutenes and polyisobutylenes, phthalates such as di-iso-undecyl phthalate (DIUP), di-iso-nonylphthalate (DINP), dioctylphthalate (DOP) and these contains a mixture of

The sprayable low application temperature hot melt adhesives of the present invention may preferably contain at least one stabilizer and/or at least one antioxidant. These compounds are added to protect the adhesive from degradation caused by reaction with oxygen induced by heat, light or residual catalysts from raw materials such as, for example, tackifying resins.

Applicable stabilizers or antioxidants encompassed herein include high molecular weight masked phenols and polyfunctional phenols such as sulfur and phosphorus-containing phenols. Masking phenols are well known to those skilled in the art and can be characterized as phenolic compounds that also contain radicals that are sterically large in close proximity to their phenolic hydroxyl groups. In particular, generally a tertiary butyl group is substituted on the benzene ring in at least one of the ortho positions relative to the phenolic hydroxyl group. The presence of such sterically large substitutional radicals near the hydroxyl group acts to retard its elongation frequency, and hence its reactivity, and thus such shielding provides the phenolic compound with its stabilizing properties. Representative masking phenols include: 1,3,5-trimethyl-2,4,6-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)-benzene; pentaerythrityl tetrakis-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate; n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate; 4,4'-methylenebis(2,6-tert-butyl-phenol); 4,4′-thiobis(6-tert-butyl-o-cresol); 2,6-di-tertbutylphenol; 6-(4-hydroxyphenoxy)-2,4-bis(n-octyl-thio)-1,3,5-triazine; di-n-octylthio)ethyl 3,5-di-tert-butyl-4-hydroxy-benzoate; and sorbitol hexa[3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionate].

Such antioxidants, commercially available from Ciba Specialty Chemicals, include the shielding phenols IRGANOX® 565, 1010, 1076 and 1726. They can be used as primary antioxidants that act as radical scavengers, either alone or in combination with other antioxidants such as phosphite antioxidants such as IRGAFOS® 168 available from Ciba Specialty Chemicals. . Phosphite antioxidants are considered secondary antioxidants and are generally not used alone. They are mainly used as peroxide decomposers. Other commercially available antioxidants include CYANOX® LTDP, available from Cytec Industries, and ETHANOX® 330, available from Albemarle Corp. It is possible for many such antioxidants to be used either alone or in combination with other such antioxidants. These compounds are added to the hot melt in small amounts, typically less than about 10% by weight, and do not affect other physical properties. Other compounds that can be added without affecting their physical properties are pigments or fluorescent agents that add color, to mention just two. Additives such as these are known to the person skilled in the art.

Other additives commonly used in hot melt adhesives may be added to the adhesive composition of the present invention to satisfy other properties and to meet specific application requirements. Such additives include, for example, fillers, pigments, rheology modifiers, dyes, ionic and nonionic surfactants, which may be incorporated into adhesive formulations in trace or large amounts depending on the purpose.

Hot melt adhesive compositions are generally prepared by blending the components in a melt at a temperature of greater than about 150° C. to about 180° C. for about 2 hours to form a homogeneous blend. A variety of blending methods are known in the art, any method that produces a homogeneous blend can be used. The blend is then cooled and can be formed into pellets or blocks for storage or transport. This pre-formed adhesive can then be reheated for application onto the substrate.

The specific combination of a tackifier, and optionally a specific polypropylene (co)polymer in combination with a wax and/or plasticizer, forms a hot melt adhesive suitable for sprayable low application temperature adhesives. The adhesive has a tan δ value greater than about 30 at 140° C., 10 rad/s. A person skilled in the art can measure the tan δ value in various ways.

Surprisingly, the sprayable hot melt adhesive is suitable for spraying at low application temperatures, while also providing high green strength, excellent bonding strength and aging performance on a variety of substrates. In addition, the sprayable low application temperature hot melt adhesive enables thin bond lines without the risk of bleed-through and burning to heat-sensitive substrates.

Adhesives made from conventional polypropylene are not suitable for spraying at low application temperatures. Many conventional polypropylene (co)polymers have high molecular weight, and melt flow rates of less than 20 g/10 min as measured at 230°C/2.16 kg, making them unsuitable as sprayable adhesives below 155°C. . In addition, adhesives made from other conventional polypropylenes having a low molecular weight, and a melt flow rate greater than 300 g/10 min as measured at 230°C/2.16 kg, exhibit sufficient cohesive strength and elasticity to provide satisfactory bonding performance. don't have Also, combining the two types of conventional polypropylene polymers in a single adhesive results in both high viscosity and poor bonding performance.

Adhesives prepared from certain polypropylene (co)polymers having melt flow rates from about 20 g/10 min to about 300 g/10 min as measured at 230° C./2.16 kg described herein provide high bonding to nonwoven and film substrates. Provides strength (adhesion). It has been found that the bond strength of adhesives made using the polypropylene (co)polymers described herein are at least an order of magnitude higher than adhesives made from conventional polypropylene (co)polymers for the same substrate. In addition, the adhesives prepared from the polypropylene (co)polymers described herein continue to exhibit excellent bond strength after the bonded laminates are exposed to aging conditions of 50° C. for 2 weeks. Typically, the bond strength of an adhesive to a substrate degrades over time with aging; The bond strength of the aged laminate-on-laminate adhesive prepared using the polypropylene (co)polymer described herein maintains bond strength similar to that of the initially formed bond. In addition, adhesives made from the polypropylene (co)polymers described herein do not gel when exposed to elevated temperatures for extended periods of time, such as 160° C. for 72 hours.

The adhesive has a Brookfield melt viscosity of from about 2,000 to about 11,000 cps at 150° C. as measured with spindle #27 according to ASTM 3236-88. Melt viscosity is the resistance to shear in the molten state, quantified as the ratio of the shear stress divided by the shear rate at any point in the flowing material. These include roll coating, painting, dry-brushing, dip coating, spraying, slot-coating, spin spraying, printing (such as inkjet printing), flexographic printing, extrusion, atomization spraying, gravure (pattern wheel transfer), electrostatic, vapor deposition, It ensures a versatile application of the adhesive onto the substrate by fiberization (spraying) and/or screen printing. This viscosity range is particularly suitable for fiberizing applications such as Signature, Omega, Control coat, Summit, Spiral and Melt blow applications and the like.

The tan δ value at 140° C. of the hot melt adhesive of the present invention, i.e., the ratio of the loss modulus G” to the storage modulus G′, is greater than about 30. The elastic modulus (G′) is an indicator of adhesive stiffness and , loss modulus (G") is an indicator of adhesive flow, the quantity values can be routinely measured using a rheometer in the art. Adhesives having a tan(δ) value greater than 30 at 140°C were found to be good indicators in determining sprayability below 155°C.

The adhesive advantageously has good green strength. Green strength is a measure of the ability of an adhesive to hold two substrates together immediately after contact, and is measured and expressed as static peel adhesion. Typically, an adhesive is sprayed onto a polymeric film substrate at a specified add-on level and then bonded to a nonwoven substrate with a specified compression pressure. Within 15 minutes of bonding, the test is performed using a static peel method commonly known in the art. Static peel times for adhesives made using the polypropylene (co)polymers described herein exceed 300 seconds, which is considered satisfactory green strength for adhesives.

Because of the excellent bonding strength, aging bonding strength and static peel adhesion of the adhesives of the present invention, they are particularly suitable for bonding substrates such as nonwovens, polymer films, elastic films or tissues to another substrate. A nonwoven web of material, such as a nonwoven woven web, may include sheets of individual nonwoven component layers bonded together using a mechanical, thermal or chemical bonding process. The nonwoven web may be formed as a flat, porous sheet made directly from individual fibers derived from molten plastic and/or plastic film. As is known in the art, suitable nonwoven web materials that may be useful in the present invention also include spunbond, meltblown, spunmelt, solvent-spun, electrospun, carded, film fibrillated, melt-film fibrillated, air-laid, dry-laid, wet-laid staple fibers, and the like, and other nonwoven web materials formed in part or wholly of polymeric fibers. The nonwoven web may be formed primarily of polymer fibers. In some instances, suitable nonwoven fiber materials include polymeric materials such as polyolefins, polyesters, polyamides, or especially PET and PBT, polylactic acid (PLA), and alkyds, polypropylene (PP), polyethylene (PE) and polybutylene ( polyolefins including PB), olefinic copolymers derived from ethylene and propylene, thermoplastic polyurethanes (TPU) and styrenic block-copolymers (linear and radical di- and tri-block copolymers such as various types of Kraton) ), polystyrene, polyamide, PHA (polyhydroxyalkanoate) and starch-based compositions including, for example, PHB (polyhydroxybutyrate), and, for example, thermoplastic starch, including, but not limited to it is not The polymers may be used as homopolymers, copolymers such as copolymers of ethylene and propylene, blends and mixtures thereof. An exemplary film may be an elastomeric polymer. Non-limiting examples of elastomeric polymers include homopolymers, block copolymers, random copolymers, alternating copolymers, graft copolymers, and the like. Particularly suitable polymers for use in the film are polypropylene and polyethylene films. Representative films include DH292 and DH276 films commercially available from Clopay Corporation of Cincinnati, Ohio. Other representative films include K11-815 and CEX-826 elastomeric films commercially available from Tredegar Film Products, Richmond, Virginia. Such materials are believed to have excellent elastic properties.

The adhesive is applied to the substrate while in its molten state and cooled to cure the adhesive layer. The adhesive product may be applied to a substrate in an amount sufficient to cause the article to adhere to another substrate by a variety of methods, including coating or spraying. Applying a minimal amount of hot melt adhesive extends life and reduces defects in heat-sensitive substrates. Although spraying is effective at controlling the amount sprayed onto a substrate compared to other methods, such as slots, sprayable hot melt adhesives place more stringent requirements.

In some embodiments, the nonwoven and film substrates are not thicker than about 50 micrometers, about 60 micrometers, or about 70 micrometers. Depending on the material and thickness of the material, the substrate is heat sensitive. Applying a high temperature adhesive on such a substrate can damage the substrate, in which case the substrate melts or deforms at the site of application of the adhesive. Therefore, it is advantageous to apply the adhesive at a lower temperature. It is also advantageous to apply a thin bond line to minimize damage to the substrate; A thin bond line reduces the bond strength of the adhesive.

The low application temperature hot melt adhesives of the present invention enable thin bond lines without bleed-through and burn hazard to heat-sensitive substrates. Because of the excellent adhesive strength, minimal amounts of adhesive can be used to form the bond. Also, due to the fast curing and high green strength of the adhesive, the bleed-through problem is minimized. In addition, the adhesives of the present invention can be applied at lower temperatures compared to conventional adhesives, thereby minimizing the risk of substrate burning and deformation.

Features of the present invention include diapers, diaper pants, baby wipes, training pants, absorbent briefs, children's care pants, swimwear, and other disposable garments; feminine care products including sanitary napkins, wipes, menstrual pads, panty liners, panty shields, tampons and tampon applicators; adult-care products including wipes, pads, containers, incontinence products and urine shields; clothing components; athletic and recreational products; Products for applying hot or cold therapies, medical gowns (i.e. protective and/or surgical gowns), surgical drapes, caps, gloves, face masks, bandages, wound dressings, wipes, covers, containers, filters, disposable garments and bed pads, absorbent medical garments, underpads; construction and packaging articles, industrial pads, including meat pads; Household convenience products including cleaning and disinfecting products, wipes, covers, filters, towels, bath tissues, facial tissues, non-woven rolls, pillows, pads, cushions, masks and body care products such as for cleaning or treating skin It makes them particularly suitable for use in absorbent articles such as articles used, lab coats, coveralls, and the like. The sprayable low application temperature adhesive is also useful in bottle labels, or other applications involving plastic bonding or removable pressure sensitive adhesive applications.

In one embodiment of the present invention, a disposable absorbent article is provided. The disposable absorbent article typically comprises (1) a liquid-permeable topsheet, (2) a liquid-impermeable backsheet to which the topsheet may be attached, (3) an absorbent structure positioned between the topsheet and the backsheet; and (4) a hot melt adhesive having the properties described herein.

Nonwovens are used commercially in a variety of applications including insulators, packaging (such as food such as meat), household wipes, surgical drapes, medical dressings, and disposable articles such as diapers, adult incontinence products, and sanitary napkins. Tissues are closely related materials in which individual fibers may or may not be chemically bonded to each other.

Representative materials suitable for use as the topsheet are liquid-permeable materials, such as spunbonded polypropylene or polyethylene having a basis weight of from about 10 to about 25 grams per square meter.

Backsheets, often used in disposable absorbent products, typically contain liquids such as water, urine, menses, or blood within the absorbent core of the disposable absorbent products and serve to protect the bedding and/or the wearer's outer garments from diluents or plasticizers. made from a liquid-impermeable material. Materials useful as backsheets for disposable absorbent articles are generally impermeable to liquids but permeable to vapors. Examples are liquid-impermeable materials such as polyolefin films, such as polypropylene and polyethylene, as well as vapor-permeable materials such as microporous polyolefin films, often referred to as respirable films.

A particularly preferred backsheet material is a film comprising a polyolefin polymer such as linear low density polyethylene and a filler. As used herein, "fillers" are particulates and other types of materials that can be added to film polymer extrusion blends and that do not chemically interfere with or negatively affect the extruded film but can be uniformly dispersed throughout the film. means including When the film is stretched during processing, the filler generally causes a network of holes to form in the film. Such apertures are generally small enough to prevent passage of liquids, but generally large enough to allow vapors to pass through the apertures. Generally, the filler will be in particulate form and will have a generally spherical shape with an average particle size in the range of about 0.1 to about 7 micrometers. Both organic and inorganic fillers may be used in the practice of the present invention, provided that they do not interfere with the film formation process. Examples of fillers include calcium carbonate (CaCO ₃ ), various types of clays, silica (SiO ₂ ), alumina, barium sulfate, sodium carbonate, talc, magnesium sulfate, titanium dioxide, zeolite, aluminum sulfate, Cellulose-type powder, diatomaceous earth, magnesium sulfate, magnesium carbonate, barium carbonate, kaolin, mica, carbon, calcium oxide, magnesium oxide, aluminum hydroxide, pulp powder, wood powder, cellulose derivatives, chitin and chitin Derivatives are included.

As will be appreciated by those skilled in the art, many modifications and variations of the present invention can be made without departing from the spirit and scope of the invention. The specific embodiments described herein are provided by way of example only, and the invention may be limited only by the terms of the appended claims, along with the full scope of equivalents to which they are appended.

[ Example ]

The present invention will be further described in the following examples, which are included for purposes of illustration and are not intended to limit the scope of the invention in any way.

Heat of fusion and maximum melting temperature were measured using DSC according to ASTM D3418-12.

The viscosity of polymers having an MFR greater than 1000 g/10 min at 230° C./2.16 kg was measured using a Brookfield viscometer, spindle #27 at 190° C. according to ASTM 3236-88.

In Table 1 below, various polypropylene (co)polymers are listed along with their comonomer, polypropylene content, melt flow rate, polydispersity (Mw/Mn), heat of fusion and melting peak. For polymers with melt flow rates greater than 1000 g/10 min at 230° C./2.16 kg, the Brookfield viscosity at 190° C. was measured and recorded.

<Table 1>

Polymer 1 (P1) had the following parameters: a melt flow rate of from about 20 to about 300 g/10 min at 230° C./2.16 kg as measured by ASTM D1238, (ii) a polydispersity (Mw/Mn) less than about 3.0 ) value, (iii) a propylene content of from about 70 to about 92 weight percent of the (co)polymer, (iv) a melting point of less than about 70° C., and (v) a heat of fusion value of less than about 20 J/g. Polymers 2-9 deviated out of at least one of these parameters.

56.5% by weight of an adhesive (Wingtack Extra), 3% by weight of a wax (H1 wax), 20% by weight of a plasticizer (Nyflex 222B) and 0.5% by weight of an anti-oxidant (Evernox) ) 10) together with 20% by weight of polypropylene (co)polymer as indicated in Table 2 to prepare an adhesive. The adhesive was prepared by mixing all the ingredients at 150 to 180° C. for about 2 hours.

The viscosity of the adhesive was measured according to ASTM 3236-88 at 140° C. and 150° C. using a standard Brookfield viscometer, spindle 27.

A TA Dynamic Mechanical Analyzer (ARES-M LS) was used to obtain tan δ from Orchestrators software version 7.2.0.4 using the temperature gradient test. For this test, steel parallel plates (316 stainless steel from TA Instruments, part # 708-00966-1) with a diameter of 25 mm and separated by a gap of about 1 mm were used. The sample was loaded and then heated to the required temperature of 160° C., and the temperature ramp was initiated once an equilibrium of 160° C. was reached. Program test data were displayed at intervals of 10 seconds. The convection oven (type Ares-LN2) was continuously refluxed using cold nitrogen gas. The cooling rate was 5 °C/min until 0 °C was reached. The convection oven was continuously refluxed with nitrogen. The frequency was maintained at 10 rad/s. The initial strain at the start of the test was 50% (at the outer edge of the plate). Accurately measurable torque was maintained throughout the test using the software's autostrain option. The options were configured such that the maximum applied strain allowed by the software was 80%. The autotransform program adjusted the strain at each temperature increment, where it was warranted to use the following procedure. When the torque was less than 19.62×10 ^-3 Nm, the deformation was reduced to 5% of the present value. When the torque exceeds 117.72×10 ^-3 Nm, it is reduced to 25% of its present value. At torques between 19.62×10 ⁻³ and 117.72×10 ⁻³ Nm, no change in strain was achieved at that temperature increment. Shear storage or elastic modulus (G') and shear loss modulus (G") were calculated from torque and strain data by software. tan δ was recorded as G"/G' at 140°C, i.e. tan δ = G″/G′ (at 140° C.).

<Table 2>

Polymer 1, Comparative Samples C and D, had a suitable viscosity range for spray applications. In addition, the tan δ values of Polymer 1, Comparative Samples C and D at 140° C. were greater than 30, indicating that these polymers were sprayable at up to 155° C. Comparative Samples A and B had significantly higher viscosities, and tan δ values of less than 30 at 140°C.

Each of the adhesive samples listed in Table 2 was subjected to an additional spraying of 2.5 gsm at 150-155° C. at a linear speed of 1000 feet per minute using a Nordson Corp signature applicator head, using a Nordson Corp signature applicator head. It was applied on DH 292 PE from Coplay Corp. Next, a second substrate (15 gsm nonwoven fabric from PGI) was applied onto the adhesive to prepare a bonded article.

The bond strength of the nonwoven to the film was measured using a tensile tester in a Model I T-peel configuration for the initial and aged samples. A suitable tensile testing machine shall provide a computer interface for universal tensile testing at constant speed, such as a Sintech 1/D tensile testing machine (MTS, Model 1500 BZF-50, USA) or equivalent. The tensioning machine shall be equipped with a high precision 222 N loading cell or equivalent. Thwing-Albert Instruments Co., Philadelphia, PA. Using a yarn precision cutter or equivalent, the sample being tested was cut into a substantially straight shape and sized to the dimensions of the sample to be tested. The sample dimensions were chosen to achieve the required deformation using the appropriate force on the instrument. Sample dimensions were approximately 2 inches wide by approximately 6 inches long. The length of the sample was aligned in the machine direction, ie the MD direction. Before testing at the same temperature, the samples were equilibrated at 23° C.±2° C. for a minimum of 1 hour. Fixtures and grips were installed using light duty jaws (flat face or rod wire could be used) sized appropriately to the dimensions of the sample being tested. The instrument was calibrated according to the manufacturer's instructions. The distance between the gripping force lines (gauge length) was 1 inch, measured using a steel ruler attached to the side of the grip. To account for the mass of the fixture and grip, the force readout on the instrument was zeroed. For the T-peel test, samples (2 inches wide times approximately 6 inches long) were prepared using the following procedure:

(1) Mark the sample using a pen by drawing a line across the 2-inch width of the sample at a location 1 inch from the sample end. (2) 6" long and 2" wide masking tape on the entire film side (Corporate Express, MFG# CEB1X60TN, pwi-inc.com from Paperworks, Inc. or equivalent) ) to fix the piece. (3) Initiate peeling of the nonwoven fibers from the film by stretching the sample in small increments in a 2 in ² area between the pen mark and the sample end. (4) Secure a piece of masking tape 4 inches long and 1 inch wide centered across the sample top 2 inches wide at the end of the stretched sample to initiate peeling, and applying pressure to bond the tape to the sample Sikkim. The tape was placed on a 2 inch wide surface opposite the side of the nonwoven. This tape will support the film portion of the t-peel sample after steps 5 and 6 have been completed. (5) Gently pull the fiber away from the film on the nonwoven side in a 2 in ² area between the pen mark and the sample end. For well-bonded samples, this can be achieved by using a rubber eraser to gently rub the sample in a direction approximately toward the pen mark. (6) Carefully peel the nonwoven from the film toward the pen mark. (7) Positioning a second piece of tape 4 inches long and 1 inch wide centered across the top 2 inches wide of the nonwoven fibers intentionally peeled from the sample to form the nonwoven portion of the T-peel sample. To perform the T-peel test, the sample is mounted on a grip in a T-peel configuration, wherein the nonwoven portion of the T-peel sample is mounted on the bottom grip and the film portion of the T-peel sample is mounted on the top grip. Mount the specimen in the grips in such a way that minimal slack is present and the force being measured is less than about 0.02 N. The samples were peeled off by moving the crosshead upwards at a constant crosshead speed of 12 in/min until each material (nonwoven fiber and film) was completely separated. During delamination, force and extension data were acquired at a rate of 50 Hz. The peel force (g) during the first 8 inch extension is reported as the Mode I bond strength.

A minimum of five samples were used to determine the average initial bond strength. The bond strengths of the initial and aged samples were measured as follows:

Bond strength [g/in] = Average peel force [g] / Specimen width [in]

The same test was performed on aged samples, in which case the sample laminates were aged at 50° C. for 2 weeks. The aged samples were then equilibrated at 23° C.±2° C. for a minimum of 1 hour before testing at the same temperature. A minimum of 5 samples were also used to determine the average aged bond strength. The initial and aged bond strengths of the adhesives are reported in Table 3.

To determine the static peel holding time, a bonded sample was prepared. The static peel retention time was measured within 15 minutes of formation of the bonded laminate. A signature applicator head was used to spray the sample adhesive onto the polymer film at 2.5 gsm addition and a rate of 1000 feet per minute, then immediately covered the nonwoven substrate with a pressing pressure of 75 psi to form a bonded laminate. The coating width was 2 inches wide. The bonded laminate was then cut 1 inch wide by 4 inches long. The length of the sample was aligned in the direction transverse to the machine, i.e. the CD direction, with the 2 in ² adhesive area centered. Static peel samples were prepared using the following procedure: The full 4-inch length sample had 1 inch without adhesive that could be easily opened on each of the top and bottom phases. Static peeling by positioning a 2 inch long and 1 inch wide masking tape centered across the top 1 inch wide of the nonwoven to secure the end of the nonwoven and securing another piece of masking tape to the end of the Poly part. A sample was formed. Samples were tested at 23°C ± 2°C. Clamp the open 1 in ² area on the bonding poly film side onto the shear tester while simultaneously clamping the open 1 in ² area of the nonwoven part. A weight of 50 grams was clamped to be suspended from the nonwoven substrate onto the surface. The time was recorded from the start of the 50 gram weight suspension until the total separation of the nonwoven from the film as the weight pulled the nonwoven down. This time is static peel, and 5 bonded specimens were tested for each sample, and the averages are listed in Table 3 below.

<Table 3>

Samples A and B were not sprayable below 155°C. Comparative samples C and D were sprayable at 150°C; The bond strength was significantly compromised. Only sample 1 was sprayable at or below 155° C. and had adequate bond strength and static peel values.

<Table 4>

RT 2315 was Rextac's PP/PE amorphous polyalphaolefin, and Eastoflex 1060 was Eastman Chemical Company's PP/PE amorphous polyalphaolefin. Samples 1 and 2 were sprayable at up to 155°C and had adequate bond strength and static peel values, whereas Sample E required a much higher temperature of 165°C to spray compared to Samples 1 and 2.

As will be appreciated by those skilled in the art, many modifications and variations of the present invention can be made without departing from the spirit and scope of the invention. The specific embodiments described herein are provided by way of example only, and the invention may be limited only by the terms of the appended claims, along with the full scope of equivalents to which they are appended.

Claims (20)

(a) (i) a propylene content of 70 to 95 weight percent of the polypropylene-polyethylene (co)polymer, (ii) a polydispersity (Mw/Mn) index of less than 3.0, (iii) 230 as measured according to ASTM D1238 a melt flow rate of 20 to 300 g/10 min at °C/2.16 kg, (iv) a melting point of less than 90 °C as measured according to ASTM 3418, and (v) a melt flow rate of 10 °C/min as measured according to ASTM D3418-12 5 to 40% by weight of a polypropylene-polyethylene (co)polymer having a heat of fusion value of less than 35 J/g at heating and cooling rates;
(b) 30 to 70% by weight of an adhesive; and
(c) optionally up to 30% by weight of a wax or plasticizer
includes,
(i) a tan(δ) value greater than 30 at 140°C, 10 rad/s, and (ii) a melt viscosity of 2,000 to 11,000 mPa·s (cps) at 150°C as measured according to ASTM 3236-88
A hot melt adhesive with The polypropylene-polyethylene (co)polymer according to claim 1, wherein the polypropylene-polyethylene (co)polymer has (i) a propylene content of 75 to 92% by weight of the polypropylene-polyethylene (co)polymer, (ii) a polydispersity index of less than 2.5, (iii) 70 A hot melt adhesive having a melting point of less than °C, and (iv) a heat of fusion value of less than 20 J/g. The adhesive of claim 1 , wherein the tackifier is selected from the group consisting of C ₅ resins, petroleum distillates, hydrogenated hydrocarbons, C ₅ /C ₉ resins, C ₉ resins, polyterpenes, rosins, hydrogenated rosins, rosin esters, and mixtures thereof. In hot melt adhesive. The hot melt adhesive of claim 1 , wherein the wax is selected from the group consisting of paraffin, microcrystalline, polyethylene, polypropylene, Fischer-Tropsch wax, oxidized Fischer-Tropsch wax, functionalized wax, and mixtures thereof. 2. The method of claim 1, wherein the plasticizer is polybutene, polyisobutylene, paraffinic oil, naphthenic oil, phthalate, benzoate, adipic acid ester, mineral oil, aliphatic oil, aromatic oil, long chain partial ether ester, alkyl mono A hot melt adhesive selected from the group consisting of esters, epoxidized oils, dialkyl diesters, aromatic diesters, alkyl ether monoesters, and mixtures thereof. According to claim 1,
(a) (i) a propylene content of 81 to 91 weight percent of the polypropylene-polyethylene (co)polymer, (iii) a melt flow rate of 40 to 150 g/10 min, (iv) a melting point of less than 65° C., and (v) ) from 15 to 25% by weight of a polypropylene-polyethylene (co)polymer having a heat of fusion value of less than 20 J/g;
(b) 50 to 60% by weight of an adhesive; and
(c) 25 to 35% by weight of a wax or plasticizer
includes,
(i) both initial and aged bond strengths at 2.5 g/m ² (gsm) addition greater than 39.4 g/cm (100 g/in), and (ii) 300 at 2.5 g/m ² (gsm) addition Green strength as a function of static peeling time in excess of seconds
A hot melt adhesive with 6. The method according to any one of claims 1 to 5,
(a) (i) a propylene content of 70 to 95 weight percent of the polypropylene-polyethylene (co)polymer, (ii) a polydispersity (Mw/Mn) index of less than 3.0, (iii) 230 as measured according to ASTM D1238 a melt flow rate of 20 to 300 g/10 min at °C/2.16 kg, (iv) a melting point of less than 90 °C as measured according to ASTM 3418, and (v) a melt flow rate of 10 °C/min as measured according to ASTM D3418-12 5 to 40% by weight of a polypropylene-polyethylene (co)polymer having a heat of fusion value of less than 35 J/g at heating and cooling rates;
(b) 30 to 70% by weight of an adhesive;
(c) 1 to 50% by weight of an amorphous poly alpha olefin polymer; and
(d) 1 to 30% by weight of wax and/or plasticizer
is essentially made up of
(i) a tan(δ) value greater than 30 at 140°C, 10 rad/s, and (ii) a melt viscosity of 2,000 to 11,000 mPa·s (cps) at 150°C as measured according to ASTM 3236-88
A hot melt adhesive with 8. The method of claim 7,
(a) (i) a propylene content of 81 to 91% by weight of the polypropylene-polyethylene (co)polymer, (ii) a polydispersity (Mw/Mn) value of less than 2.5, (iii) 40 to 150 g/10 min. 5 to 25 weight percent of a polypropylene-polyethylene (co)polymer having a melt flow rate, (iv) a melting point of less than 65° C., and (v) a heat of fusion value of less than 15 J/g;
(b) 40 to 60% by weight of an adhesive;
(c) 1 to 20% by weight of an amorphous poly alpha olefin polymer; and
(d) 25 to 35% by weight of wax and/or plasticizer
includes,
(i) both initial and aged bond strengths at 2.5 g/m ² (gsm) addition greater than 39.4 g/cm (100 g/in), and (ii) 300 at 2.5 g/m ² (gsm) addition Green strength as a function of static peeling time in excess of seconds
A hot melt adhesive with An article comprising the adhesive according to claim 1 sandwiched between two substrates. 10. The article of claim 9, wherein the substrate is selected from the group consisting of nonwovens, polymeric films, elastic films, and tissues. 10. The article of claim 9, wherein the article is a diaper, training pants, absorbent panty, sanitary napkin, medical gown, mead pad or disinfecting wipe. 1) spraying the hot melt adhesive composition according to claim 1 onto at least a portion of the first substrate at an additional level of 0.1 to 10 g/m ² (gsm) at a temperature of 155° C. or less;
2) applying a second substrate on the hot melt adhesive; and
3) cooling the hot melt adhesive composition to room temperature
A method of forming a bonded article comprising: delete delete delete delete delete delete delete delete